1. Field of the Invention
The invention relates to a position adjustment mechanism and a method thereof, and more particularly, to a mechanism and method for adjusting the position of a mounting plate relative to the tray of an optical disk drive.
2. Description of the Prior Art
In recent years, personal computers have changed from calculation oriented to multimedia oriented. Therefore storage devices for storing a big amount of video information are improved continuously. An optical disk drive that can read and write information to optical disk has become a mainstream product in the market. A pickup head of the optical disk drive emits laser beams with specific wavelengths and power to read information stored in the optical disk or write information into the optical disk. In specification, the main products of optical disk are compact disks (CD) and digital versatile disks (DVD). The optical disks also can be divided into read-only optical disks, write-once optical disks, and rewritable optical disks in application. The optical disk drives can also be divided into video disk players and CD burners.
FIG. 1 is a schematic diagram of a main body 10 of an optical disk drive according to the prior art. The main body 10 comprises a mounting plate 12, a spindle motor 14 positioned on the mounting plate 12 for providing a motive power to rotate an optical disk put on the spindle motor 14, a main guide bar 16 and a sub guide bar 18 positioned in opposite side on the mounting plate 12, and a pickup head 20 connected to the main guide bar 16 and the sub guide bar 18 by a sliding way along the direction of the main guide bar 16 and the sub guide bar 18 to read or write information to the optical disk. Following is the description of the operation method of the optical disk drive by explaining the theory of reading information manner.
When the optical disk drive is going to read information of a specific track on the optical disk, the pickup head 20 will slide along the direction of the main guide bar 16 and the sub guide bar 18 to a corresponding position and emit laser beams having a wavelength, with the spindle motor 14 rotating, to read the information from the specific track. However, an inaccuracy may occur during fabricating the optical disk drive, so that the two ends of the main guide bar 16 and the sub guide bar 18 will have different heights. As a result, the distance between the pickup head 20 and the surface of the optical disk will be indefinite when the pickup head 20 slides along the main guide bar 16 and the sub guide bar 18. The indefinite distance results in that the emission power of the pickup head 20 is hardly controlled, even in errors or failures of reading information.
Referring to FIGS. 2 and 3, FIG. 2 is a schematic diagram of a reverse side of the main body 10 shown in FIG. 1, wherein an optical disk is positioned on the spindle motor 14, and FIG. 3 is a section view of the main body 10 shown in FIG. 2. In FIG. 3, assuming that the two ends of the main guide bar 16 and the sub guide bar 18 have different heights, there is an angle θ1 between the sliding direction of the pickup head 20 (the dual-arrow 26) and the horizontal surface of the optical disk. As shown in FIG. 3, the distance between the pickup head 20 and the surface of the optical disk as the pickup head 20 slides to a position close to the spindle motor 14 is different from the distance as the pickup head 20 slides to a position far away from the spindle motor 14.
In the prior art, to solve the problem resulting from the indefinite distance between the pickup head 20 and the optical disk, a plurality of height adjusting mechanisms are installed on the ends of the main guide bar 16 and the sub guide bar 18, such as three tuning screws 22 in FIG. 1. After the main body 10 of the optical disk drive is assembled, those tuning screws 22 will be adjusted individually according to the different heights of the main guide bar 16 and the sub guide bar 18 to insure that the directions of both of the main guide bar 16 and the sub guide bar 18 are parallel with the surface of the optical disk so as to prevent the problem of the indefinite distance between the optical disk surface and the pickup head 20.
However, the inaccuracy occurred during the fabrication and assembling process of the optical disk drive not only results in the angle θ1 between the sliding direction of the pickup head 20 and the surface of the optical disk, but also results in other problems when the main body 10 is further assembled to a tray of the optical disk drive. Please refer to FIG. 4. FIG. 4 is a schematic diagram of the tray 28 of the optical disk drive. The main body 10 is assembled onto the tray 28. The assembling method is to install a plurality of screws through the dampers 24 (such as rubber pads) and corresponding through holes, to thread nuts onto the screws, and to thread the screws into the corresponding bores 30 on the tray 28 so as to fasten the mounting plate 12 to the tray 28, as shown in FIG. 5, which is a schematic diagram of the assembled main body 10 and the tray 28.
Please refer to FIGS. 6 and 7. FIG. 6 is a schematic diagram in a reverse side of the main body 10 and the tray 28 shown in FIG. 5 wherein the optical disk is positioned on the spindle motor 14. FIG. 7 is a section view of the main body 10 and the tray 28 shown in FIG. 6. Another problem resulting from the inaccuracy of the assembling process is that an error angle between the main body 10 (including the mounting plate 12 and the spindle motor 14) and the tray 28 occurs. It results in an angle θ2 between the surface of the optical disk located on the spindle motor 14 and the tray 28, which causes the outer portion of the optical disk to collide with the tray 28 when the optical disk rotates. The above-mentioned problem is especially serious in thin-type optical disk drives of common notebook computers because the space in a thin-type optical disk drive is especially small.